Adolescents' relationships to siblings and mothers: A multivariate genetic analysis.

Abstract

This article addresses concerns raised by M. C. Neale (1999) in his commentary on the D. A. Bussell et al. (1999) Nonshared Environment in Adolescent Development (NEAD) study. These concerns fall into two categories: (a) model assumptions and sample design and (b) testing of alternative models. The validity of the assumptions of quantitative genetic models is a concern for all researchers in this area. Discussion of those assumptions in this reply is brief and focuses on those most relevant to the NEAD sample. The two alternative models proposed by Neale were designed to provide alternatives to the large shared environmental effect found in the original report of Bussell et al. Because these alternative models did not provide a better fit, the appropriateness of Bussell et al.'s basic model and the importance of shared environmental influences for explaining the association among family subsystems are supported.

Genetic and environmental influences on adolescent substance use and abuse

“…In our sample, shared environmental factors accounted for 41% to 66% of the variance in liability to illicit substance use and abuse. Our findings are clearly consistent with the estimates of shared environmental influence of 47% for lifetime drug use and from 68% to 85% for lifetime marijuana use in the Virginia study of adolescent twins [Maes et al, 1999] Although the behavioral genetic literature suggests that there is little effect of shared environment on many characteristics in adults [Plomin and Daniels, 1987], behavioral genetic studies of parental and sibling relationships during childhood and adolescence [Elkins et al, 1997;Bussell et al, 1999] indicate moderate shared environmental influence during these ear-lier developmental stages. In a study of adolescent adoptees [McGue et al, 1996], there were significant effects of unrelated siblings on each other's substance use, even though the environment that reared-together adoptees shared was relatively unimportant for most aspects of adolescent adjustment.…”

Adolescent Development in Interpersonal Context

“…On average, shared family environment explains only 5% to 10% of the variance in psychological behaviors and attitudes (Collins et al, 2000). Research findings also indicate that variation in the family climate, as opposed to the adolescent behavior or personality trait in question, across sibling and parent-adolescent relationships is explained more by shared influences than nonshared ones (Bussell et al, 1999).…”

Observation of Externalizing Behavior During a Twin-Friend Discussion Task

“…Additional reports (not presented in Table 1) from aggregated NEAD data have assessed change in antisocial symptoms over time (e.g., Neiderhiser, Reiss, & Hetherington, 1996;T. O'Connor, Neiderhiser et al, 1998) and the covariation between antisocial behavior and parenting practices (e.g., Bussell, Neiderhiser, Pike, Plomin et al, 1999;Neiderhiser et al, 1999;Neiderhiser, Pike, Hetherington, & Reiss, 1998;Pike et al, 1996). An adoption study corroborates the aggregated NEAD results; Jary and Stewart (1985) found genetic effects, environmental effects, and evocative G 3 E correlations on child antisocial behavior using a composite measure of diagnostic symptoms, and self-, parent, and observer report.…”